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Abstract

Hard Water and Cleansers: An In-Vitro Study of the Effects on Immature Reconstructed Human Epidermis

Background: Barrier function impairment resulting from increased exposure to daily use of surfactants in the presence of hard water (HW) has been identified as a relevant factor to the development of atopic dermatitis (AD), especially in infants.

Objectives: To investigate the effect of HW as such or in the presence of surfactants on skin barrier development as it occurs during infancy, using a 3D reconstructed immature (not fully differentiated) human epidermis model.

Materials and Methods: Reconstructed Human Epidermis (RHE) starting at the 13th day of differentiation was exposed to HW alone or in the presence of surfactants (Sodium Dodecyl Sulphate and a commercial cleansing oil) for 2 days (two topical exposure per day) followed by two days of recovery. The barrier structure and functional modifications have been assessed by evaluating epidermal morphology (H&E), tight junctions barrier functionality (TEER measure), proteins’ expression of claudin-1, filaggrin and involucrin by immunohistochemistry, inflammation by transcriptional activity of TNF-α and RHE ultrastructure (TEM analysis).

Results: HW itself has modified the differentiation process without influencing the barrier function structure (Claudin 1 was not significantly affected) but in presence of SDS, HW has induced inflammation, morphological modification in particular cell swelling and SC lamellar structure damages leading to a severe modification to the barrier structure in the final epidermal differentiation. The effects of the hard water are reduced in the presence of a mild cleansing oil including emollients.

Conclusion: The results obtained using the in-vitro RHE model are in agreement with the clinical observations reported in the literature regarding the detrimental effect of the hard water on the skin of infants. Moreover, the in-vitro model can be a useful tool to evaluate the effects of both surfactant and cleansing formulation on impaired skin.